I have wanted to do 9MM AR build for some time and finally decided to get off my a** and start this project. The good part(I think)is that I have complete Bushy lower. Which upper should I use? Which mag block is the best choice? What magazine is the most functional?

what system do you want to use? Colt or Oly? what type of mags do you want to use? Colt, sten, uzi, suomi or other?
Since you are asking a general question let me recommend that you read all of the threads in this forum and use the search button to search for this very topic here in the AR15 section of this site.

Blessed are the peacemakers, for they will be called sons of God.

I'd rather be sorry for something I've done then for something that I didn't do.

I would go with a RRA upper
It is based on the COLT system.
You will need a 9mm hammer(unless you get the bolt ramped) and 9mm buffer.
You can get a upper for under $400.
As far as mags and adaptors, I beleive that most people use UZI mags.
There are 2 types of adaptors people use.
(1) Hytech - no mods to mags- UZI only
(2) ASA or Garrison - Colt mags or modified Uzi
You can answer ALL of your questions by reading the 2 stickys at the top of this forum.
Good luck.

I found complete Colt 9MM upper and was going to pick up HY-TECH mag block because of the ability to use stock UZI mag until I read about the fitting required and raised mag button mod needed. How does everyone rate the following alternatives with the Colt upper?
ASA
Garrison
Hahn
RRA

Originally Posted By mallcop:
I found complete Colt 9MM upper and was going to pick up HY-TECH mag block because of the ability to use stock UZI mag until I read about the fitting required and raised mag button mod needed. How does everyone rate the following alternatives with the Colt upper?
ASA
Garrison
Hahn
RRA

View Quote

You are going to have to notch the uzi mags to work with those blocks. Thats running around $8 a mag to notch. Is it worth it for you? Also it appeares Hy-Tech is modifying their design on the block around the end of January. CAn you wait til then or do you wish to perform the modifications to the block yourself?

Blessed are the peacemakers, for they will be called sons of God.

I'd rather be sorry for something I've done then for something that I didn't do.